Recovery of sandy campinaran soils degraded by sand mining to unleash the ecological restoration of this ecosystem

Abstract

Sand mining is an activity that causes undesirable environmental impacts on the soil, fauna and flora, leading to the loss of habitats, biodiversity and various ecosystem services. In the Metropolitan Region of Manaus, the main mining activity is the extraction of sand in Campinaranas from sandy soils. Campinaranas are vegetable portions in the middle of the forest, with typical flora and fauna, forming islands of endemic species, from herbaceous to arboreal. Although they have less diversity than the tropical forests that surround them, these islands have great ecological importance, since they are rich in species unique to this ecosystem, also providing relevant ecosystem services like replacement of aquifers and carbon storage. Despite the intense environmental impact, the need for this material in abundance for civil construction and the lack of substitutes on the necessary scale, make sand extraction a very intense economic activity today. Therefore, controlled and rational mining becomes necessary, with the consequent recovery of degraded ecosystems. However, the ecological restoration of mined areas is a a costly activity, which requires a set of elaborate techniques, especially based on the recovery of the soil in the initial phase. The recovery of soils from the mined areas of Campinaranas is even more challenging because it is fragile, highly erodible, poor in nutrients, which occur as entrapments within the forest environment, whose capacity for recolonization and natural regeneration is very restricted. The traditional technique employed to promote the restoration of areas explored in sand mining projects in the region is the direct planting of seedlings of native species, which due to soil degradation, is not proving to be effective. Despite the importance and urgency of this topic (recovery of the soils of Campinaranas), no studies were found that focused on the recovery of the degraded soils of Campinarana by sand mining activities and, therefore, the great majority of the initiatives of recovery of campinaranas mined were not successful. Therefore, the main objective of this proposal is to identify an adequate and economically viable technical procedure for the recovery of degraded soils in Campinaranas after sand exploration. Initially, the characterization of preserved campinaran soils as reference ecosystems will be carried out, as well as the characterization of degraded soils (or mining floor) in Campinaranas after sand mining, through morphological, physical, chemical and soil macrofauna attributes. With the characterization of the degradation of these soils, using the reference ecosystems, the need to recover these soil features will be quantified. Thus, for the recovery of degraded soils, we will implement experiments in greenhouse, and later, in the field, in order to select which treatment is most suitable for the recovery of degraded soils in Campinaranas, by sand extraction. During the experiments, the following materials will be used: a) addition of top layer of top soil, collected from reference areas; b) planting commercial species of green manure; c) addition of residues from açaí processing; d) addition of tanned sawdust; e) correction of acidity and fertilization, according to the results of chemical characterization. These treatments are focused on replacing the organic matter necessary to fix nutrients, which will trigger the trajectory of soil recovery. This study will produce unprecedented data, which will allow to understand the levels of degradation of the impacted soils, to select indicators of the soil quality, the rate of loss of natural vegetation, know which species are established after leaving the area, as well as select the most suitable treatment for the recovery of degraded soils. Finally, based on these results, we will prepare an initial protocol for the restoration of areas of campinaranas degraded by sand mining, which will represent an excellent service for society. (AU)